USB Input Distorted

[Earthdance]

I am using a USB analogue audio mixer to mix music (from phone acting as mp3 player) and voice (from head mic). The resultant signal is fed into the laptop via USB3 socket. I have tested this by recording the Zoom meeting and by joining the meeting from another room. The result is awful and totally unusable. The music cuts in and out, when the voice starts the music cuts out completely, but even without the voice parts of the music signal are missing and the tune is unrecognisable. 

There is nothing wrong with the mixer as I have recorded the signal into the laptop using Audacity and it is fine. I have turned off all the "gimmicks" on Zoom such as echo cancelling, turned on original sound, set the sound to raw, and basically every combination I can find but nothing works. My laptop is Intel i7 12th gen running Win 11 which is completely up to date. 

Has anyone had a similar problem?